Crosslinkable composition comprising modified aminoepoxy resins - II

ABSTRACT

A crosslinkable composition of matter is provided, which comprises first and second chain extended diepoxide resins, one or both of which are modified by reaction with hydroxy functional secondary amine and one or both of which are modified by reaction with certain secondary amine terminated or carboxy terminated butadiene acrylonitrile copolymer resin. The first resin, diene functional aminoepoxy resin, and the second resin, blocked dieneophile functional aminoepoxy resin, are co-reactive at elevated cure temperature. The diene functional aminoepoxy resin comprises the reaction product of diepoxide with amine functional diene chain extending reactant and, optionally, monofunctional end-capping reactant such as monohydroxy functional diene, and certain modifying agents. The blocked dieneophile functional aminoepoxy resin comprises the reaction product of diepoxide with amine functional blocked dieneophile chain extending reactant and, optionally, monofunctional end-capping reactant such as monohydroxy functional blocked dieneophile and certain modifying agents. The composition may further comprise crosslinking agent reactive with hydroxy functionality of the resins. The crosslinkable composition of matter is useful in coatings and other applications, especially cathodic electrocoating compositions.

This is a division of application Ser. No. 679,962, filed Dec. 10, 1984,now U.S. Pat. No. 4,617,348.

TECHNICAL FIELD

The invention relates to certain diene-functional aminoepoxy resins andcertain dieneophile-functional aminoepoxy resin, which resins arecoreactive at elevated cure temperatures and to thermosettingcompositions of matter comprising such resins. According to certainpreferred embodiments, this invention relates to use of such resincompositions to form corrosion protective coatings. This inventionespecially relates to one-component solvent based primer coatingcompositions comprising such resins and to aqueous coating compositionsadapted for use in cathodic electrodeposition processes.

RELATED APPLICATIONS

This application is related to application Ser. No. 565,798, now U.S.Pat. No. 4,559,393, Ser. No. 566,063, now U.S. Pat. No. 4,565,852, andSer. No. 566,068, now U.S. Pat. No. 4,582,880, each filed Dec. 27, 1983;application Ser. No. 680,112, filed Dec. 10, 1984, now U.S. Pat. No.4,619,977, entitled CROSSLINKABLE COMPOSITION COMPRISING AMINO EPOXYRESIN - IV; application Ser. No. 680,411, filed Dec. 10, 1984, nowabandoned, entitled CROSSLINKABLE COMPOSITION COMPRISING MODIFIEDAMINOEPOXY RESINS - I; application Ser. No. 679,977, filed Dec. 10,1984, now U.S. Pat. No. 4,639,493, entitled CONJUGATED DIENE FUNCTIONALMODIFIED AMINOEPOXY RESINS I; application Ser. No. 679,975, filed Dec.10, 1984, now U.S. Pat. No. 4,657,979, entitled BLOCKED DIENEOPHILEFUNCTIONAL MODIFIED AMINOEPOXY RESINS; and application Ser. No. 679,783,filed Dec. 10, 1984, now abandoned, entitled EPOXYAMINE COMPOSITIONS FORELECTRODEPOSITION OF COATINGS ON A SUBSTRATE - I. In addition, thefollowing commonly assigned applications each relate todiene/dieneophile chemistry in compositions suitable for thermosetting,coatings and the like: Ser. No. 455,678 now U.S. Pat. No. 4,514,548, andSer. No. 455,718 now U.S. Pat. No. 4,514,549, filed Jan. 1, 1983, Ser.No. 456,067 now U.S. Pat. No. 4,515,926, and Ser. No. 456,068 now U.S.Pat. No. 4,513,125, filed Jan. 6, 1983 and Ser. No. 458,119 now U.S.Pat. No. 4,508,879, filed Jan. 14, 1983.

BACKGROUND ART

Coating compositions are known which are suitable for application to asubstrate, for example, by spraying, dipping, electrodeposition or thelike, which coating compositions are then cured by baking the coatedsubstrate at an elevated temperature. Typically, such coatingcompositions comprise resinous materials or blends of resinousmaterials, in some cases together with suitable crosslinking agentreactive with such resinous materials at elevated temperature.

In regard to electrodeposition of coatings, the process is welldescribed in the art. Typically, an aqueous bath containing the coatingcomposition is placed in contact with an electrically conductive anodeand an electrically conductive cathode, and upon the passage of electriccurrent (normally direct current) between the anode and the cathode, anadherent film of the coating composition is deposited. Depending uponthe nature of the coating composition, the coating may be deposited atthe anode or at the cathode. The voltage applied may vary from as lowas, for example, one volt to as high as, for example, 500 volts orhigher. Typically, however, the voltage used ranges from about 50 toabout 400 volts.

A wide variety of electrodepositable resins are known to the skilled ofthe art. For example, a number of water-soluble, water-dispersible, orwater-emulsifiable poly-carboxylic acid resins can be electrodeposited.Some of these resins include, for example, reaction products or adductsof a drying oil or semidrying oil fatty acid ester with a di-carboxylicacid or anhydride; interpolymers of a hydroxyalkyl ester of anunsaturated carboxylic acid, unsaturated carboxylic acid, and at leastone other ethylenically unsaturated monomer; alkyd-amine vehicles, thatis vehicles containing an alkyd resin and an amine-aldehyde resin; andmixed esters of resinous polyols. In U.S. Pat. No. 3,991,028 to Irwin etal, electrodepositable compositions are disclosed which comprise awater-dispersion of a hydrolyzed polyepoxide in combination with aninterpolymer of a hydroxyalkyl ester, an unsaturated acid and at leastone other monomer, and an amine-aldehyde resin. The use of a hydrolyzedpolyepoxide is said to provide improved properties and to avoidagglomeration of the coating composition. In U.S. Pat. No. 4,026,855 toParekh et al, a coating composition is disclosed to be adaptable for usein electrodeposition or as a water-based coating for applicatin by sprayor dip coating methods. The composition comprises an aqueous dispersionof (A) an ungelled modified crosslinking agent comprising certainaminoplast crosslinking agent modified by reaction with a non-resinouscompound containing an hydroxyl-group bearing carboxylic acid, and (B) awater dispersible non-gelled polymeric material carrying a cationiccharge and containing at least one class of reactive groups selectedfrom carboxyl groups, alcoholic hydroxy groups and amide groups and alsocontaining amino groups, and (C) an acid solubilizer. In U.S. Pat. No.4,033,917 to Sekmakas et al, certain copolymers of polyethylenicallyunsaturated epoxy-amine adducts are disclosed and also stable aqueousdispersions containing same and also the electrodeposition of suchaqueous dispersions at the cathode of a unidirectional electricalsystem. Specifically, amine functional polymers dispersible in waterwith the aid of a solublizing acid are said to be provided bycopolymerizing (A) certain ethylenically unsaturated hydroxy functionalamine adduct free of epoxy groups; and (B) copolymerizablemonoethylenically unsaturated monomers, a portion of which isamine-functional. The copolymer is said to be stably dispersible inwater at certain pH and to be electrodepositable at the cathode,optionally together with an aminoplast curing agent to provide coatingswhich can be cured, ususally by exposure to elevated temperature. U.S.Pat. No. 3,471,388 to Koral is directed to a cathodic electrocoatingcomposition which incorporates an aminoplast crosslinker (e.g.,butylated melamine) with an aminated polymer containing hydroxy groups.Numerous suitable hydroxy-containing aminated polymers are suggestedwhich have capability to crosslink with an aminoplast crosslinkingagent. One such suggested polymer is the reaction product of apolyfunctional amine with a polyfunctional epoxy compound. Thepolyhydroxy polymers are said to be disperable in water upon addition ofsuitable acid such as acetic acid.

Additional teaching directed to coating compositions suitable for use inelectrocoating processes is provide in U.S. Pat. No. 4,159,233 to Tingeet al; U.S. Pat. No. 4,057,523 to Blank; U.S. Pat. No. 4,182,831 toHicks; U.S. Pat. No. 4,192,932 to Dickie, which patent is assigned tothe assignee of the present application; U.S. Pat. No. 4,192,929 toBloomfield, which patent is assigned to the assignee of the presentapplication; U.S. Pat. No. 4,202,746 to Lee et al; and U.S. Pat. No.4,072,536 to Otsuki et al.

It is a general objective of the present invention to provide acomposition of matter adaptable for use in coating compositions,including compositions adapted for use in solvent-based sprayablecoating compositions, compositions adapted for use in electrodepositioncoating compositions, and compositions adapted for use in themanufacture of adhesives, molding compounds and textile treating resinsand the like. Additional objects and aspects of the present inventionwill be apparent from the following description thereof.

DISCLOSURE OF THE INVENTION

The present invention provides a crosslinkable composition of matterwhich composition comprises first and second chain extended aminoepoxyresins, each being co-reactive with the other at elevated curetemperatures. At least one of the resins is modified by reaction withmodifying agent comprising hydroxy functional secondary amine,preferably secondary alkanolamine, and at least one is modified byreaction with second modifying agent selected from the group consistingof certain secondary amine terminated butadiene acrylonitrile copolymerresins, certain carboxy terminated butadiene acrylonitrile copolymerresins, and any mixture thereof. Preferably both aminoepoxy resins aremodified both by the hydroxy functional secondary amine and thebutadiene acrylonitrile copolymer.

The aforesaid first aminoepoxy resin is conjugated diene functionalaminoepoxy resin of number average molecular weight about 1000-18,000,comprising the reaction product of suitable diepoxide reactant withfirst reactant comprising chain extending reactant, specifically, aminefunctional diene, particularly a di-secondary amine functional bis-dieneor, more preferably, a mono-primary amine functional diene such as, forexample, furfuryl amine or a compatible mixture thereof. The dienefunctional aminoepoxy resin preferably is end-capped. That is,preferably such first reactant further comprises suitable monofunctionalreactant, most preferably monofunctional conjugated diene reactant suchas, for example, mono-secondary amine functional conjugated diene,mono-hydroxy functional conjugated diene which is preferred, or anycompatible mixture thereof. (Obviously, the term "monofunctional" inthis usage is intended to mean only a single functionality substantiallyreactive with epoxy functionality and is not exclusive of conjugateddiene functionality.) End-capping reactants, with which the diepoxidecan be reacted either subsequently or simultaneously with the aminefunctional diene, include, for example, furfuryl alcohol and otherswhich will be apparent to the skilled of the art in view of the presentdisclosure. Other end-capping reactants which preferably are reactedsubsequent to the reaction of the diepoxide with the amine functionaldiene, for example 2-hydroxymethyl-1,3-butadiene, will also be apparent.Whether the reaction of the diepoxide resin with the amine functionaldiene would more preferably be carried out prior to or simultaneouslywith the end-capping reaction will be apparent to the skilled of the artin view of the present disclosure, considering the relative reactivityof the reactants and the desired molecular weight range of the dienefunctional aminoepoxy resin. As noted above, the diene functionalaminoepoxy resin may be modified by reaction with (i) modifying agentcomprising hydroxy functional secondary amine, (ii) second modifyingagent comprising certain butadiene acrylonitrile copolymer resins, or(iii) both, as further discussed below.

The aforesaid second resin is blocked dieneophile functional aminoepoxyresin of number average molecular weight about 1000-18,000, comprisingthe reaction product of suitable diepoxide resin with second reactantcomprising chain extending reactant, specifically, amine functionalblocked dieneophile, such as a di-secondary amine functional bis-blockeddieneophile or, more preferably, a mono-primary amine functional blockeddieneophile, or a compatible mixture thereof. Preferably such aminefunctional blocked dieneophile is a mono-primary amine functionalblocked ene, such as, for example, amino maleamic acid. The blockeddieneophile functional aminoepoxy resin preferably is end-capped. Thatis, preferably such second reactant further comprises suitablemonofunctional end-capping reactant as further discussed below. As notedabove, the blocked dieneophile functional aminoepoxy resin may bemodified by reaction with (i) modifying agent comprising hydroxyfunctional secondary amine, (ii) second modifying agent comprisingcertain butadiene acrylonitrile copolymer resin, or (iii) both, asfurther discussed below.

The two aminoepoxy resin components of the invention are used preferablyin molar ratio of about 1:2 to about 2:1. Most preferably they are usedin stoichiometric amounts.

The crosslinkable composition of the invention is particularly useful incoating compositions and according to preferred embodiments furtherdiscussed below is readily adaptable for use in solvent-based coatingcompositions and in aqueous-based electrodeposition coatingcompositions. Coatings provided by the present invention are found to behighly resistant to solvents and humidity and to provide exceptionalcorrosion protection for the underlying substrate. Also, in using theaminoepoxy resins of the invention in electrocoating applications, thepolybutadiene acrylonitrile resin second modifying agent is found toimprove the throwing power of the electrocoat bath, especially at lowvoltages, and to improve the corrosion protection provided by the curedcoating. The invention also is particularly advantageous in that itprovides coatings which cure at relatively low temperature.Crosslinkable compositions provided by the invention also may be used inthe manufacture of low pressure laminates, adhesives, molding compounds,textile treating resins and the like.

According to a significantly advantageous aspect of the invention, themolecular weight of the aminoepoxy resins is readily controllable tosuit their intended use. Thus, for use in a cathodic electrocoatingcomposition, for example, the diene functional aminoepoxy resin of theinvention is readily provided having preferred number average molecularweight (Mn) of about 1000-12,000. For use in solvent-based sprayablecoating compositions, such resin is readily provided having preferrednumber average molecular weight (Mn) of about 1000-3000. Such molecularweight control is achieved by selection of diepoxide reactant havingappropriate epoxide equivalent weight and by adjusting the molar ratioof diepoxide to amine functional diene to mono-hydroxy functional diene(or other monofunctional end-capping reactant). Lower molecular weightresin is provided as this ratio approaches 2:1:1, respectively; highermolecular weight resin is provided as it approaches 1:1:0. Control ofthe molecular weight of the blocked dieneophile functional aminoepoxyresin is provided in the same manner. Of course, in preparing the dienefunctional aminoepoxy resin and the blocked dieneophile functionalaminoepoxy resin, it should be understood that sufficient excessdiepoxide reactant is employed in the preparation of at least one ofthem to provide epoxy functionality for reaction with the aforesaidmodifying agent, and sufficient excess diepoxide reactant is employed inthe preparation of at least one of them to provide epoxy functionalityfor reaction with the aforesaid second modifying agent.

The crosslinkable composition of the present invention can be adaptedfor use in solvent-based sprayable primer coating compositions. Suchprimer compositions can be used, for example, to form heat curable,highly alkali resistant primer coatings on automotive vehicle bodypanels. Such compositions comprise substantially gel-free dienefunctional aminoepoxy resin, as described above, and substantiallygel-free blocked dieneophile functional aminoepoxy resin, as describedabove, each preferably of number average molecular weight (Mn) about1000-3000. The compositions can be thinned to desired viscosity withsuitable solvent such as, for example, methyl amyl ketone.

The composition of the present invention is particularly suitable foruse in cathodic electrodeposition. For such use, the compositioncomprises (i) substantially gel-free diene functional aminoepoxy resin,as described above, preferably of number average molecular weight (Mn)about 1000-12,000, at least partially neutralized with a solubilizingacid, typically an organic acid such as, for example, acetic acid or thelike, and (ii) substantially gel-free blocked dieneophile functionalaminoepoxy resin, as described above, preferably of number averagemolecular weight (Mn) of about 1000-9000, also at least partiallyneutralized. The at least partially neutralized resins are dispersedtogether in aqueous solvent. Such coating composition will deposit aheat curable coating at the cathode in an electrodeposition coatingprocess according to techniques well known to the skilled in the art.

Other features and advantages of the present invention will become moreapparent from the following detailed description including the preferredembodiments and best mode of the invention.

DETAILED DESCRIPTION OF THE INVENTION Diene Functional Aminoepoxy ResinDiepoxide Reactant

The conjugated diene functional aminoepoxy resin comprises the reactionproduct of any of a wide variety of diepoxide reactants, for examplealiphatic and aromatic diepoxides, with amine functional diene. Suitablediepoxide reactant has number average molecular weight of about300-8,000, preferably about 300-4,000. In general the epoxide equivalentweight is selected to suit the intended use of the final composition.Thus, for sprayable solvent-based coating compositions a lowercomposition viscosity is desirable. For such use it is generallypreferable to employ diepoxide having epoxide equivalent weight of about150-1000. In comparison, for example, cathodic electrodepositioncompositions of the invention preferably have higher viscosity and forsuch use diepoxides having epoxide equivalent weight of about 150-2000are generally preferred.

The diepoxide is preferably free of carboxy ester moieties linking theepoxide groups, since such carboxy ester-free diepoxides have been foundto provide cured coatings according to the invention which aresignificantly more alkali resistant and provide significantly enhancedcorrosion protection to the underlying substrate.

One class of suitable diepoxides includes the BisphenolA-epichlorohydrin resins. These are commercially available as, forexample, Epon 828, 1001 or 1004 (trademarks) marketed by Shell ChemicalCompany, Houston, Tex., U.S.A. Suitable diepoxides may contain aromaticgroups, such as benzene nuclei, at a preferred average of at least aboutone, more preferably at least about two, for each terminal epoxy group.Especially suitable are Bisphenol A-epichlorohydrin resins comprising upto 10 or more bis-phenol moieties within the epichlorohydrin reactionproduct backbone, for example those of number average molecular weightup to about 8000, preferably 300-4000.

Aliphatic diepoxides, particularly lower molecular weight aliphaticdiepoxides, including cycloaliphatic diepoxides are used preferably inconjunction with aromatic diepoxides to modify coating properties.Certain lower molecular weight aliphatic diepoxides used alone mayproduce coatings which are relatively more humidity sensitive. Suitablealiphatic diepoxides include, for example, the reaction product ofepihalohydrin with aliphatic diols such as glycol, epoxidizedpolybutadienes, vinylcyclohexenedioxide and dipentene dioxide. Stillfurther, hydrogenated Bisphenol A-epichlorohydrin products may also beemployed.

Numerous additional suitable diepoxides are commercially available orreadily prepared using well known techniques and commercially availablestarting materials, and these will be apparent to the skilled of the artin view of the present disclosure. Compatible mixtures of any of thesecompounds also are suitable.

Amine Functional Diene Chain Extending Reactant

Amine functional dienes suitable for use in preparing the resin of thepresent invention are those comprising conjugated double bonds,particularly, those suitable for Diels Alder cycloaddition reaction atelevated temperature with ene-functionality or with other dieneophilefunctionality. Suitable amine functional dienes include many well knownto the skilled of the art. Preferred are monoprimary amine functionaldienes, preferably of molecular weight about 70-300 and preferablycomprising no functionality substantially reactive with the diepoxide,other than the N-hydrogens. Exemplary monoprimary amine functionaldienes include furfuryl amine, 2-aminomethyl-1,3-butadiene, and the likeand mixtures thereof. Suitable di-secondary amine functional bis-dieneswill be apparent to the skilled of the art in view of the presentdisclosure and can be prepared using well known techniques andcommercially available reactants.

According to one most preferred embodiment, the monoprimary aminefunctional diene reactant is of the general formula: ##STR1## wherein R³is a divalent organic linking moiety containing no ester groups andpreferably no functionality substantially reactive with the otherreactants under reaction conditions experienced in the preparation ofthe aminoepoxy resin.

Preferably, as noted above, the chain-extended reaction product ofdiepoxide with amine functional diene is end-capped. The end-cappingagent preferably is monohydroxy functional conjugated diene. Suitablemonohydroxy functional dienes include many well known to the skilled ofthe art and preferably is of molecular weight about 70-300 andpreferably comprises no functionality substantially reactive with thediepoxide other than the hydroxy group. Exemplary monohydroxy dienesinclude furfuryl alcohol and 2-hydroxymethyl-1,3-butadiene and the likeand any compatible mixture thereof. The end-capping agent also can be amonoamine reactant, preferably monoamine functional conjugated dienereactant. Typically, a mono-secondary amine is used to provide trueend-capping of the aminoepoxy resin. It will be understood by theskilled of the art, however, that mono-primary amine also can be used asan "end-capping agent" according to the present invention, although acertain degree of chain extension may result. Mono-primary amineend-capping agent can be used as one means of increasing to some extentthe molecular weight of the product resin. Suitable monohydroxyfunctional dienes and monoamine functional dienes include those of thegeneral formula: ##STR2## wherein:

R is a monohydroxy functional hydrocarbon moiety or a monoaminefunctional hydrocarbon moiety, respectively, which preferably comprisesno functionality substantially reactive with the diepoxide reactantother than the hydroxy or amine functionality, respectively;

X⁰ is ##STR3## or the like, wherein R¹ is hydrogen straight, branched orcyclo alkyl, aryl, arylalkyl or the like, and each R² is the same ordifferent and is selected from hydrogen, straight, branched or cycloalkyl, aryl, arylalkyl, or the like; and

X¹, X², X³, X⁴ and X⁵ are the same or different and each is hydrogen,straight, branched or cyclo alkyl, aryl, arylakyl, or the like, or X¹and X⁵ together are alkylene, --O--, or --NR¹ -- wherein R¹ is asdefined above, or like divalent group (resulting in a cyclic dienemoiety).

The diepoxide reactant is reacted with the end-capping agent, if any,and the amine functional diene according to methods well known to theskilled in the art. Accordingly, for example, a stoichiometric amount ofan equimolar mixture of monohydroxy functional diene end-cappingreactant and amine functional diene chain extending reaction are mixedwith the diepoxide reactant and heated to reaction temperature,typically above 120°-150° C., until substantially all epoxidefunctionality has reacted. As noted above, however, the molar ratio ofreactants can be varied to provide diene functional aminoepoxy resin ofdesired molecular weight. Also, as further discussed below, the resinmay be modified by reaction with a modifying agent and/or a secondarymodifying agent, in which case sufficient diepoxide reactant is employedfor reaction therewith.

The reaction product, that is, the aminoepoxy resin, comprises, onaverage, at least one diene moiety per molecule. Each diene moiety willbe available for reaction with a dieneophile moiety of the blockeddieneophile functional aminoepoxy resin during heat curing of acomposition according to the invention. More preferably, the dienefunctional aminoepoxy resin provides, on average, about two or more,most preferably about 3-10 diene moieties per molecule to provide goodcrosslinking.

Blocked Dieneophile Functional Aminoepoxy Reactant

The blocked dieneophile functional aminoepoxy resin preferablycomprises, on average, about two or more, preferably at least about 3,most preferably about 3-10, blocked dieneophile groups per molecule. Theblocked dieneophile groups are capable of reacting with the dienemoieties of the diene functional aminoepoxy resin upon curing thecomposition at elevated temperature, typically about 100° C.-200° C.Preferably the dieneophile moiety is an ene moiety although othersuitable dieneophile moieties will be apparent to the skilled of the artin view of the present disclosure. The diene functional aminoepoxy resinand the blocked dieneophile functional aminoepoxy resin are found toafford well cured coatings when employed in compositions together inratio of between about 1:0.1 to about 0.1:1 equivalents, respectively,with lower molecular weight resins of the invention preferably used inratio of about 2:1 to about 1:2.

The blocked dieneophile functional aminoepoxy resin preferably isprovided as the reaction product of suitable mono-primary aminefunctional blocked dieneophile with suitable diepoxide reactantincluding any of those diepoxides described above for preparation of thediene functional aminoepoxy resin. Accordingly, the dieneophilefunctional resin also provides nitrogen sites for at least partialneutralization upon addition of neutralizing acid, many of which acidsare well known to the art, as described above. Such at least partiallyneutralized dieneophile functional resin is readily dispersed intoaqueous solvent for preparation of cathodic electrodepositioncompositions.

The mono-primary amine functional blocked dieneophile reactant ispreferably the reaction product of maleic anhydride, unsaturatedlactone, or a compatible mixture thereof with a suitably reactive dieneand a suitably reactive diamine. The diene reactant acts as a reversibleblocking agent for the dieneophile functionality and such reaction canbe carried out prior to, during or after the reaction with the diamine.The diene reactant preferably has a boiling point at or below the curetemperature of the coating composition such that it will be driven fromthe coating composition during cure thereof, and not compete with thediene functionality of the diene functional aminoepoxy resin forreaction with the blocked dieneophile functional aminoepoxy resin. Tomaximize yield of mono-primary amine functional blocked dieneophile, itis preferred to add the anhydride or lactone reactant slowly to anexcess of diamine reactant.

According to one prefered embodiment, the monoprimary amine functionalblocked dieneophile reactant comprises amino maleamic acid,specifically, the reaction product of suitable diamine with3,6-endoxo-1,2,3,6-tetrahydrophthalic anhydride. The named anhydride iscommercially available, for example from Aldrich Chemical Co.,Milwaukee, Wisc., U.S.A. and also can be prepared as the reactionproduct of furan with maleic anhydride.

More generally, suitable amine functional blocked dieneophile reactantcomprises the reaction product of (i) suitable diamine, and (ii)suitable conjugated diene reversible blocking agent, with (iii) enereactant selected from the group consisting of maleic anhydride,suitable unsaturated lactones or the like or any compatible mixturethereof, wherein the lactone preferably is selected from those of thegeneral formula: ##STR4## wherein each R' is selected independently fromH, C₁ -C₅ alkyl, C₁ -C₅ hydroxy alkyl and the like, and y is preferablyabout 1-4. Numerous suitable diamines are commercially available andwill be apparent to the skilled of the art in view of the presentdisclosure. Suitable diamines include those of the general formula H₂N--R⁵ --NH₂ wherein R⁵ is any divalent organic linking moiety of atleast two carbons, preferably 2-15 carbons, which is substantiallyunreactive (under conditions experienced by the amine functional blockeddieneophile reactant in the preparation of the aminoepoxy resin) withthe other reactants. Included are branched, straight and cyclicaliphatic diamines, aromatic diamines and arylaliphatic diamines.Exemplary diamines include isophorone diamine which is preferred in viewof the difference in reactivity of the two amine groups resulting inhigher yield of the desired product, 1,4-butanediamine,1,5-pentanediamine, 1,6-hexanediamine, and a compatible mixture of anyof them. Other preferred diamines include those of molecular weightabout 80-300 which comprise no substantially reactive functionalityother than amine. Exemplary such diamines include 1,2-ethylenediamine,1,3-propanediamine, the isomers of toluene diamine and the like and acompatible mixture of any of them.

Suitable conjugated diene blocking agents include numerous commerciallyavailable dienes readily apparent to the skilled of the art in view ofthe present disclosure. Included are any sufficiently reactiveconjugated aliphatic, cyclic aliphatic, and heterocyclic dienes whichwill liberate or de-block from the dieneophile moiety at the curetemperature of the coating composition. The diene blocking agent shouldbe substantially unreactive with the other reactants except for thedieneophile functionality of the ene reactant. Exemplary conjugateddiene blocking agents include furan which is preferred since itde-blocks at approximately 120° C., conjugated cycloalkadiene such as1,3-cyclopentadiene and 1,3-cyclohexadiene, conjugated alkadienepreferably of about 4-10 carbons, for example, 1,3-butadiene,2-methyl-1,3-butadiene, and the like and a compatible mixture of any ofthem. The reactions described above for preparation of the blockeddieneophile functional aminoepoxy resin can be conducted according tomethods well known to the skilled of the art. It should be noted thatwhere symmetrical diamine is employed, such as 1,6-hexanediamine, ratherthan diamine wherein one amino group is substantially more reactive thanthe other, such as isophorone diamine, there can be a portion of thediamine reactant in which both amine groups remain unreacted due toreaction of both amine groups of another portion of the diaminereactant. To prevent subsequent unwanted amine reactions and gelling,substantially all unreacted diamine should be removed from the reactionproduct. Removal of diamine can be done by methods known to the skilledof the art, for example by thorough rinsing of the reaction product withdimethoxy ethane or other suitable solvent.

In the reaction of the amine functional blocked dieneophile reactantwith the diepoxide reactant, an additional reactant can be employed, anend-capping reactant, which preferably is substantially unreactive withthe amine functional blocked dieneophile reactant and which provides asingle functionality such as amino, more preferably hydroxy, which isreactive with the epoxy functionality of the diepoxide reactant (or ofthe chain extended aminoepoxy intermediate reaction product). Suchadditional reactant is preferably a monofunctional blocked dieneophile.(Monofunctional in this usage meaning only a single functionalitysubstantially reactive with epoxy functionality and not being exclusiveof blocked dieneophile functionality.) Most preferred is the reactionproduct of a suitable diene blocking agent, as described above, such asfuran, cyclopentadiene, or the like, with monohydroxy functionaldieneophile such as, for example, hydroxypropyl methacrylate, methylolmaleimide or the like or a compatible mixture thereof. Since suchmonofunctional end-capping reactant provides only end-capping and notchain-extending reaction (except to the extent provided by amono-primary amine end-capping reactant as discussed above in connectionwith the diene functional aminoepoxy resin) with the diepoxide reactant,blocked dieneophile functional aminoepoxy resin of lower molecular wightcan be provided according to this embodiment. Such lower molecularweight resin is particularly advantageous for use in sprayablesolvent-based coating compositions. Diepoxide reactant, amine functionalblocked dieneophile reactant and monofunctional end-capping reactant areemployed preferably in ratio of about 2:1:1 to about 1:1:0 equivalents,respectively, with the latter ratio providing higher molecular weightreaction product. As noted above, however, the blocked dieneophilefunctional aminoepoxy resin may be modified by reaction with a modifyingagent and/or a second modifying agent, in which case sufficientdiepoxide reactant is employed for reaction therewith.

Modifying Agent

According to one characterizing aspect of the invention, one or both ofthe two co-reactive aminoepoxy resins is prepared using diepoxidereactant in excess of that to be reacted with the amine functional dienechain extending reactant or amine functional blocked dieneophile chainextending reactant, as the case may be, and with the end-cappingreactant, if any. Sufficient diepoxide reactant is employed to makeavailable epoxy groups for reaction with the above-mentioned modifyingagent. Preferably about 10-20% of the total epoxy functionality isreacted with the modifying agent. That is, for either or both the dienefunctional aminoepoxy resin and the blocked dieneophile functionalaminoepoxy resin the molar equivalent ratio of modifying agent secondaryamine functionality to diepoxide reactant (or aminoepoxy intermediatereaction product) epoxy functionality is from about 0.1:1 to about0.2:1, respectively.

The modifying agent comprises hydroxy functional secondary amine havinga total of up to about 20 carbons per amino nitrogen. More preferably,at least about 75 mole percent of the modifying agent comprises at leastone and preferably two primary hydroxyl groups, each hydroxyl group on acarbon atom being at least one carbon removed from any amino nitrogen.Preferred secondary amine reactants include, for example,alkylalkanolamine, dialkanolamine, N-alkanolaniline and the like and acompatible mixture of any of them, wherein each alkyl moiety and eachalkanol moiety has from one to about ten carbons, more preferably one toabout six carbons. Most preferred are the C₁ -C₅ dialkanolamines,especially diethanolamine, in view of their ready commercialavailability, low cost, and ease of reaction with the preferredpolyepoxides. While not wishing to be bound by theory, it is presentlyunderstood that each hydroxy group contributed by the modifying agent tothe resin product is available for polar-polar interaction with aqueoussolvent, thereby enhancing the dispersibility of the resin in aqueoussolvent and rendering the aqueous dispersion more stable. It is believedto be consistent with such explanation that dialkanolamine bearing twoprimary hydroxy groups is found to provide exceptionally good results.

A preferred class of hydroxy functional secondary amine modifying agentsincludes those of general formula: ##STR5## wherein each R" is selectedindependently from straight or branched chain monovalent aliphaticmoieties of up to about 10 carbons each, at least one and preferablyboth R" being substituted by hydroxy on a primary carbon atom that isnot adjacent to any amino nitrogen. R" also can form with the nitrogenpart of a heterocyclic ring compound, such as a six member ring. Morepreferably, both R" are independently alkanol of up to 7 carbons each,even more desirably up to 4 carbons each.

The diepoxide reactant or the previously chain extended intermediatereaction product of the diepoxide reactant with amine functional dienereactant (or with amine functional blocked dieneophile reactant) and thehydroxy functional secondary amine modifying agent are reacted underconditions that allow opening of the epoxy ring by amino nitrogen toprovide a gel-free reaction product. Suitable reaction conditions andtechniques are well known to the skilled of the art and will be apparentfrom the present disclosure. Thus, for example, the reaction mediumpreferably comprises non-aqueous medium that may be of diverse butpreferably polar character and serves to maintain contact of reactants,to control reaction speed, to maintain desirable viscosity and toperform other functions well known in the art. Thus, suitable solventsand diluents for the reaction medium include aromatic and aliphatichydrocarbons, ethers, ketones such a methylamyl ketone, n-amyl ether,xylene, oxygenated solvents such as cellosolves, for example, butylCellosolve acetate, hexyl Cellosolve acetate, and the like includingmixtures of these. Elevated reaction tempertures may be employed tofaciliate reaction between the epoxy functional resin and the modifyingagent. Preferably, the reaction conditions are chosen such that there isonly one reaction between the intermediate reaction product and themodifying agent, specifically, that between an epoxy group and theN-hydrogen of the modifying agent.

Second Modifying Agent

According to another characterizing aspect of the invention, one or bothof the two co-reactive aminoepoxy resins is prepared using sufficientdiepoxide reactant for reaction with a second modifying agent. That is,diepoxide reactant is used in excess of that to be reacted with theamine functional chain extending reactant (diene functional or blockeddieneophile functional, as the case may be), end-capping reactant, ifany, and the aforesaid first modifying agent, if any. It should beunderstood that at least one of the two co-reactive aminoepoxy resins ismodified by the above-described modifying agent and at least one of thetwo resins, either the same one or the other one, is modified by thesecond modifying agent. Either or both of the two aminoepoxy resins maybe modified by reaction with both the hydroxy functional secondary aminemodifying agent and the below-described second modifying agent. For usein electrodeposition of coatings, it is preferred that both resins bemodified by reaction with the first modifying agent, hydroxy functionalsecondary amine, for the improved bath stability provided thereby. Inview of the somewhat harsher reaction conditions and reaction timeneeded for reaction with the second modifying agent, as now discussed,it will be preferred for most applications that only the dienefunctional aminoepoxy resin be modified by reaction with the secondmodifying agent. This avoids potential deblocking of the blockeddieneophile functional aminoepoxy resin during reaction thereof with thesecond modifying agent. Of course, it will be recognized that the secondmodifying agent can be reacted with the diepoxide reactant prior to theamine functional blocked dieneophile reactant. Since the secondmodifying agent is in the nature of an end-capping agent, however, itpreferably is reacted last. Also, reacting it last avoids potentialepoxy-epoxy reactions and gellation due, again, to the somewhat harsherreaction conditions employed.

The second modifying agent is selected from the group consisting ofsecondary amine terminated butadiene acrylonitrile copolymer resins,carboxy terminated butadiene acrylonitrile copolymer resins, andmixtures thereof, which resins have number average molecular weight ofabout 1400-4400, preferably about 3400-3600, and amine or carboxyequivalent weight of about 700-2200, preferably about 800-1200. Itshould be recognized that in addition to two terminal amine groups, orcarboxy groups, the copolymers may bear additional such groups pendantfrom the copolymer chain. Numerous suitable second modifying agents arecommercially available or are readily prepared using available materialsand well known techniques and will be apparent to the skilled of the artin view of the present disclosure. Suitable carboxy terminated secondmodifying agent can be prepared, for example, according to methods wellknown to the skilled of the art by copolymerization of acrylonitrilemonomer with butadiene monomer. Thus, for example, free radialpolymerization can be carried out accoridng to well known techniquesusing, for example, monomeric azodicyano valeric acid initiator.Preferably the acylonitrile monomer contributes about 10-27% by weightof the butadiene acrylonitrile copolymer. The corresponding secondaryamine terminated second modifying agent can be readily prepared byreacting the aforesaid carboxy terminated polymerization product withsuitable amine such as, for example, n-aminoethyl piperazine or thelike. The secondary amine terminated butadiene acrylonitrile copolymersare preferred, especially when the aminoepoxy resin is to be used in anelectrocoating composition since the amino nitrogens are believed to aidin solubilizing the resin upon acid neutralization thereof.

Suitable second modifying agents include, for example, the groupconsisting of butadiene acrylonitrile copolymer according to formula I:##STR6## wherein x on average is about 3-7, y on average is about 1, mon average is about 6-11 and T and T' are selected independently fromcarboxy and secondary amine bearing moiety. According to one preferredembodiment, the additive resin is a copolymer according to formula Iwherein T and T' each is ##STR7## and where x on average is about 5, yon average is about 1, and m on average is about 7.

Suitable second modifying agents also are commercially available.Commercially available secondary amine terminated butadieneacrylonitrile resins include, for example, the "Hycar" ATBN (trademark)series available from B. F. Goodrich Chemical Company, Cleveland, Ohio,of which ATBN - 1300×16 is generally preferred. It has a Brookfieldviscosity at 27° C. of 2350 poise, a total amine equivalent weight of900 and acrylonitrile content of 16%. Commerically available carboxyterminated butadiene acrylonitrile copolymer resins suitable for use assecond modifying agent include, for example, the "Hycar" CTBN(trademark) series and "Hycar" CTBNX (trademark) series available fromB. F. Goodrich Chemical Company, Cleveland, Ohio. The "Hycar" CTBN resinis a butadiene acrylonitrile copolymer having terminal carboxyl groupswhich may be represented structurally as follows: ##STR8## wherein onthe average x=5, y=1 and m=10. It has a Brookfield viscosity at 27° C.of 1,310 poise, an average number molecular weight of 3,080, anequivalent weight per carboxyl group of 1,885, an equivalent weight ofcarboxyl group per hundred parts of polymer of from 0.04 to 0.08 and acarboxyl group functionality of 1.735. The "Hycar" CTBNX resin is abutadiene acrylonitrile copolymer having terminal and pendant carboxylgroups. It has a Brookfield viscosity at 27° C. of 1,500, an averagenumber molecular weight of about 3,365, an equivalent weight percarboxyl group of about 1,540, an equivalent weight of carboxyl groupper hundred parts of polymer of from 0.05 to 0.09 and a carboxyl groupfunctionality of 2.34. Other carboxy and secondary amine terminatedbutadiene acrylonitrile copolymers sitable for use as second modifyingagents will be apparent to the skilled of the art in view of the presentdisclosure. Other suitable carboxy and secondary amine terminatedbutadiene acrylonitrile copolymers for use as the second modifying agentwill be apparent to the skilled of the art in view of the presentdisclosure.

The use of second modifying agent according to the present invention isfound to provide highly significant advantages, particularly in thoseembodiments wherein the aminoepoxy resins are employed in anelectrocoating composition. Specifically, such compositionsincorporating the aminoepoxy resins modified by the above describedcarboxy or, more preferably, secondary amine terminated butadieneacrylonitrile copolymer resin are found to be far better stabilized.Thus, for example, such compositions have better shelf life and betterresist spontaneous, in-the-bath gelling. Moreover, such compositionshave been found to produce thicker films, to tolerate higher operatingvoltages and to have significantly improved throwing power. Followingcuring at elevated temperature, the cured coating has been found to haveimproved surface appearance. In addition, resistance to corrosion,especially resistance to condensing humidity, is significantly improved,most notably for coatings cured at lower temperatures. Accordingly, thepresent invention is seen to provide a significant economic advantageand to be an important advance in the art.

The chain extending reactant (amine functional blocked dieneophile oramine functional diene, as the case may be), end-capping reactant, ifany, modifying agent, if any, and second modifying agent, if any, arereacted with the diepoxide reactant in any suitable order orsimultaneously in preparing the two aminoepoxy resins of the invention.It will be within the skill of the art to select suitable molar ratios,in view of the relative reactivity of the reactants, to achieve thedesired degree of diene or blocked dieneophile functionality in theproduct aminoepoxy resin. Likewise, for the end-capping reactant,modifying agent and second modifying agent, it will be within the skillof the art to select suitable reactant molar ratios, in view of theirrelative reactivities, to produce an aminoepoxy resin product having thedesired number average molecular weight and having the desired degree offunctionality.

The diene functional aminoepoxy resin and the blocked dieneophilefunctional aminoepoxy resin can be prepared by (a) first reacting anexcess of suitable diepoxide reactant with the amine functional (dieneor blocked dieneophile) chain extending reactant, the hydroxy functionalsecondary amine modifying agent, if any, and end-capping reactant, ifany, and (b) subsequently reacting with the butadiene acrylonitrilecopolymer resin second modifying agent. As noted above, care must beexercised in exposing the blocked dieneophile functionality to thereaction conditions used for reacting the second modifying agent.Suitable reaction conditions for reaction of diepoxide (or a previouslychain-extended, end-capped and/or modified intermediate reactionproduct) with the second modifying agent typically would be about60°-80° C. for 3-4 hours. If the butadiene acrylonitrile copolymer resinsecond modifying agent is reacted after the blocked dieneophile chainextending reactant, then preferably it is reacted at temperatures notexceeding about 90° C., more preferably not exceeding about 80° C.

As noted above, the modifying agent preferably is used in amount (i.e.,reactant molar ratio) sufficient to react with approximately 10-20% ofthe total epoxy functionality of the diepoxide reactant. The secondmodifying agent is used in amount sufficient to constitute from aboutone weight percent to about 30 weight percent of the aminoepoxy resinreaction product. Preferably the second modifying agent is used inamounts of about 5-20 percent of total resin weight, most preferablyabout 10 percent. As noted above, it will be within the skill of the artto select molar ratios for the modifying agent and second modifyingagent, in view of the relative reactivity of each, to achieve thedesired degree of reaction. It also will be within the skill of the artusing known methods to remove unreacted components from the aminoepoxyreaction product. Preferably the aminoepoxy resin product contains lessthan about 20% of the original epoxy group unreacted, and typically willhave less than about 10% unreacted epoxy groups.

Crosslinking Agent

The blocked dieneophile functional aminoepoxy resin prepared accordingto the manner described above provides free hydroxy groups as a resultof the amine/epoxy reactions. The diene functional aminoepoxy resin alsomay comprise hydroxy functionality as described above. In addition, thehydroxy functional secondary amine modifying agent contributes hydroxyfunctionality. Therefore, according to one embodiment of the inventionthe crosslinkable composition further comprises suitable crosslinkingagent reactive with such hydroxy groups. Numerous such crosslinkingagents are well known to the skilled of the art and include, forexample, any of a variety of aminoplast crosslinking agents, forexample, partially alkylated melamines (melamines formaldehyde resinsmodified by alcohols), for example, partially methylated melamines andbutylated melamines, polyalkyl ethers of the polymethylol melamines, forexample, hexamethoxy methylmelamine; urea formaldehyde condensatemodified by alcohol, for example, paraformaldehyde and trioxane;polymethylol compounds of hexamethylene diurea; polycarboxylic acid suchas adipic acid and the dimethylol amide and methylol ether thereof;tetramethylolhydrazodicarbonamide; polymethylol compounds ofpolycaprolactam and methylol ethers thereof; and the like and acompatible mixture of any of them. Butylated melamines are preferredsince they are readily commercially available and provide suitablecrosslinking reactivity with the aminoepoxy resins of the invention.

Also suitable are blocked polyisocyanate crosslinking agents. As usedherein "blocked polyisocyanate" means an isocyanate compound containingtwo or more isocyanato groups, each of which has been reacted with ablocking agent which will prevent reaction of the isocyanate group atroom temperature with compounds that conventionally react with suchgroups, and at least some of which will permit that reaction to occur athigher (cure) temperatures. In general, the blocked polyisocyanate maybe prepared by reacting a sufficient quantity of an active hydrogencontaining blocking agent with the polyisocyanate to insure thatsubstantially no free isocyanato groups are present.

The proper proportion of blocked polyisocyanate crosslinking agent todiene functional aminoepoxy resin and blocked dieneophile functionalaminoepoxy resin will depend, in part, upon the degree of hydroxyfunctionality of such resins, the properties desired in the coating tobe produced and, in part, upon the desired cure response of the coatingcomposition (which will depend, in turn, upon the baking schedule to beused in curing the coating composition) and, in part, upon the desiredstorage stability of the composition, that is, upon the desired shelflife. Accordingly, the amounts of such crosslinker that can be usedvaries considerably. However, it will be within the skill of the art inview of the present disclosure to provide blocked polyisocyanatecrosslinking agent in suitable amounts. Blocked polyisocyanates ofnumerous types may be employed in the compositions of the invention.Particularly suitable blocked polyisocyanates, which will be discussedfurther hereinafter, include blocked polymethylene polyphenolisocyanates, isocyanurate ring containing blocked polyisocyanates andcertain oligoester modified blocked polyisocyanates.

In the preparation of the blocked polyisocyanate crosslinking agent, anysuitable organic polyisocyanate may be used. Representative examplesinclude the aliphatic compounds such as trimethylene, tetramethylene,pentamethylene, hexamethylene, 1,2-propylene, 1,2-butylene,2,3-butylene, 1,3-butylene, ethylidene and butylidene diisocyanates; thecycloalkylene compounds such as 1,3-cyclopentane, 1,4-cyclohexane, and1,2-cyclohexane diisocyanates; the aromatic compounds such asm-phenylene, p-phenylene, 4,4'-diphenyl, 1,5-naphthalene, and1,4-naphthalene diisocyanates, the aliphatic-aromatic compounds such as4,4'-diphenylene methane, 2,4- or 2,6-tolylene, or mixtures thereof,4,4'-toluidine, and 1,4-xylylene diisocyanates; substituted aromaticcompounds such as dianisidine diisocyanate, 4,4'-diphenyletherdiisocyanate and chlorodiphenylene diisocyanate; the triisocyanates suchas triphenyl methane-4,4'4"-triisocyanate, 1,3,5-triisocyanate benzeneand 2,4,6-triisocyanate toluene; the tetraisocyanates such as4,4'-diphenyldimethyl methane-2,2',5,5'tetraisocyanate; and thepolymerized polyisocyanates such as tolylene diisocyanate dimers andtrimers, and the like.

In addition, the organic polyisocyanate may be a prepolymer derived froma polyol including polyether polyol or polyester polyol, includingpolyethers which are reacted with excess polyisocyanates to formisocyanate-terminated prepolymers. The polyols may be simple polyolssuch as glycols, e.g., ethylene glycol and propylene glycol, as well asother polyols such as glycerol; tri-methylolpropane, pentaerythritol,and the like, as well as mono-ethers such as diethylene glycol,tripropylene glycol and the like and polyethers, i.e., alkylene oxidecondensates of the above. Among the alkylene oxides that may becondensed with these polyols to form polyethers are ethylene oxide,propylene oxide, butylene oxide, styrene oxide and the like. These aregenerally called hydroxyl-terminated polyethers and can be linear orbranched. Examples of polyethers include polyoxyethylene glycol,polyoxypropylene glycol, polyoxytetramethylene glycol,polyoxyhexamethylene glycol, polyoxynonamethylene glycol,polyoxydecamethylene glycol, polyoxydodecamethylene glycol and mixturesthereof. Other types of polyoxyalkylene glycol ethers can be used.Especially useful polyether polyols are those derived from reactingpolyols such as ethylene glycol, diethylene glycol, triethylene glycol,1,4-butylene glycol, 1,3-butylene glycol, 1,6-hexanediol, and theirmixtures; glycerol, trimethylolethane, trimethylolpropane,1,2,6-hexanetriol, pentaerythritol, dipentaerythritol,tripentaerythritol, polypentaerythritol, sorbitol, methyl glucosides,sucrose and the like with alkylene oxides such as ethylene oxide,propylene oxide, their mixtures, and the like.

A particular class of aromatic polyisocyanates which may be employed inthe novel solvent based coating compositions of the invention arepolymethylene polyphenol isocyanates having the formula: ##STR9##wherein x equals 1 to 3. The compounds, sold under the tradename "PAPI"by the Upjohn Chemical Company of Kalamazoo, Mich., are particularlyuseful in compositions of the invention, resulting in compositionsexhibiting desirable toughness in the final cured coating.

The active hydrogen containing blocking agents which are reacted withthe above described organic diisocyanates may be selected from numerousblocking agents which will be apparent to those skilled in this art.Preferred blocking agents include, for example, those selected from thegroup consisting of (i) aliphatic, cycloaliphatic and aromatic alkylmonoalcohols; (ii) hydroxyl amines; (iii) oximes; (iv) lactams; and (v)triazoles. Any suitable aliphatic, cycloaliphatic or aromatic alkylmonoalcohol may be used as a blocking agent in accordance with thepresent invention. For example, aliphatic alcohols, such as methyl,ethyl, chloroethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl,3,3,5-trimethylhexyl, decyl, and lauryl alcohols, and the like may beemployed. Suitable cycloaliphatic alcohols include, for example,cyclopentanol, cyclohexanol and the like, while aromatic-alkyl alcoholsinclude phenylcarbinol, methylphenylcarbinol, and the like. Minoramounts of even higher molecular weight relatively non-volatilemonoalcohols may be used, if desired, to serve as plasticizers in thecoatings provided by the invention. Examples of hydroxyl amines whichmay be employed as blocking agents include ethanol amine and propanolamine. Suitable oxime blocking agents include, for example,methylethylketone oxime, acetone oxime and cyclohexanone oxime. Examplesof lactams which may be used as blocking agents are e-caprolactam,q-butyrolactam and pyrrolidone, while suitable triazoles includecompounds such as 1,2,4-triazole, 1,2,3-benzotriazole, 1,2,3-tolyltriazole and 4,5-diphenyl-1,2,3-triazole. Particularly preferred activehydrogen containing blocking agents are methylethyl ketoxime and2-ethylhexanol.

(i) Isocyanurate Ring Containing Blocked Isocyanate Compounds

Within the scope of the above general class of blocked polyisocyanatecrosslinking agents, a particular class or type of blockedpolyisocyanate crosslinking agent which may be employed in the coatingcompositions of the invention comprises isocyanurate ring containingblocked isocyanate compounds. In general, these blocked polyisocyanatesmay be formed by blocking with the aforementioned blocking agents. Thesecompounds may be formed by cyclotrimerization of difunctionalisocyanates. Usually, the reaction does not stop in this stage andcontinues through the formation of polyfunctional oligomers or a mixtureof such oligomers with a portion of the pure trifunctionalpolyisocyanate. Mixtures of trifunctional product and variouspolyfunctional oligomers are commercially available.

A particularly desirable blocked polyisocyanate crosslinking agent isthe blocked form of the pure trifunctional isocyanurate represented bythe following formula: ##STR10## wherein each L is selectedindependently from the group consisting of aliphatic, cycloaliphatic andaromatic groups and combinations thereof and B is the residue of anactive hydrogen containing blocking agent. More specifically, thiscompound is disclosed in U.S. patent application Ser. No. 368,178 filedApr. 14, 1982, the disclosure of which is hereby incorporated byreference.

(ii) Oligoester Modified Blocked Polyisocyanates

Still further particular blocked polyisocyanates useful as crosslinkingagents in the coating compositions of this invention are oligoestermodified blocked polyisocyanates prepared from a particular class ofoligoester diols and triols. A first type of such oligoester modifiedblocked polyisocyanate is prepared from organic diisocyanates whereinone isocyanato group is more reactive than the other, with the morereactive isocyanato first being blocked with a blocking agent and theremaining isocyanato group then being reacted with hydroxylfunctionality of an oligoester diol or triol as referred to above. Thesecond type of oligoester modified blocked polyisocyanate may beprepared by reacting oligoester diols from the aforementioned class ofoligoesters with an excess of organic diisocyanate so as to form anisocyanato terminated prepolymer followed by blocking of the terminalisocyanato groups of the prepolymer with an active hydrogen containingblocking agent. Each of these materials is particularly useful in thecompositions of the invention and produces final cured coatingcompositions exhibiting good flexibility.

Oligoesters of the type employed in the preparation of thesecrosslinking agents are described in U.S. Pat. No. 4,322,508 issued Mar.30, 1982, the disclosure of which is hereby incorporated by reference.The hydroxy functional oligoesters within the useful class of materials(i) have a number average molecular weight (Mn) between about 150 andabout 3000, preferably between about 230 and about 1000, (ii) bear 2 or3 hydroxyl groups per molecule, and (iii) are formed by anesterification reaction between a carboxylic acid and an epoxide. Theesterification reaction products are selected from the group consistingof:

(a) the esterification reaction product of polycarboxylic acid, i.e.,carboxylic acid bearing 2 or more carboxyl groups, and monoepoxide;

(b) the esterification reaction product of polyepoxide, i.e., a compoundhaving 2 or more epoxide groups, and monocarboxylic acid, preferablycontaining no ethylenic unsaturation, and bearing no hydroxyfunctionality;

(c) the esterification reaction product of hydroxy functional carboxylicacid and monoor polyepoxide, preferably monoepoxide;

(d) the esterification reaction product of mono-carboxylic acid andhydroxy functional mono or poly-epoxide, preferably monoepoxide; and

(e) mixtures of (a)-(d).

As noted above, the first type of oligoester modified blockedpolyisocyanate crosslinking agent is prepared by (i) reacting organicdiisocyanate bearing one isocyanato group which is more reactive thanthe other with a sufficient amount of an active hydrogen containingblocking agent to react substantially with all of the more reactiveisocyanate groups, thus providing a half-blocked diisocyanate and (ii)reacting this half-blocked intermediate with the above discussedoligoester. The organic diisocyanates employed in this synthesis, aswell as the active hydrogen containing blocking agents, are discussedabove in connection with the preparation of the isocyanurate ringcontaining blocked isocyanate crosslinking agents useful in compositionsof the invention. The organic polyisocyanate-blocking agent adductintermediate is formed by reacting a sufficient quantity of the blockingagent with the organic diisocyanate to insure that one of the two --NCOgroups on the diisocyanate is reacted. The reaction between the organicdiisocyanate and the blocking agent is exothermic and the diisocyanateand the blocking agent are preferably admixed at temperatures no higherthan about 80° C., preferably below about 50° C., to minimize theexothermic effect.

The diisocyanate/blocking agent intermediate is next reacted with theoligoester diol or triol described above so as to react substantiallyall free or unblocked isocyanato groups of the intermediate withhydroxyl groups of the oligoester. This reaction is carried outdesirably at a temperature of about 80°-120° C.

As also discussed above, the second type of oligoester modified blockedpolyisocyanate crosslinking agent useful in the novel solvent basedcoating compositions of the invention is prepared by reacting an excessof organic diisocyanate with an oligoester diol from the above describedclass of oligoesters followed by reaction of the terminal isocyanatogroups formed on the resultant prepolymer with an active hydrogencontaining blocking agent as described above so as to react withsubstantially all the isocyanato groups. The diisocyanate startingmaterial is used in excess in amounts sufficient to insure that theintermediate is isocyanate terminated. Therefore, it is preferable thatthe organic diisocyanates and the dihydroxy functional oligoester bereacted in a molar ratio of from greater than 1:1 up to 2:1. Numerousdiisocyanates of the type described hereinbefore may be employed in thepreparation of this intermediate. While it is not necessary that oneisocyanato group be more reactive than the other, the preparation ofthis type of crosslinking agent does not preclude the use of suchmaterial.

Other suitable crosslinking agents will be apparent to the skilled ofthe art in view of the present disclosure.

In the crosslinkable compositions of the invention, if an aminoplast orblocked polyisocyanate crosslinking agent is employed, it may beadvantageous in certain embodiments or for certain applications toinclude in the composition any of a variety of compatible catalystsknown to the skilled of the art to catalyze reaction of same withhydroxy, for example, for aminoplast crosslinking agent,paratoluenesulfonic acid, phosphoric acid, phenol acid phosphate, butylmaleate and the like or a compatible mixture of any of them. Exemplarycatalysts for blocked polyisocyanate crosslinking agent include theLewis acid catalysts and others known to the skilled of the art. Inaddition, a flow control agent, for example, polybutylacrylate; awetting agent, for example, silicone; pigments; a pigment dispersent;and/or a corrosion inhibitor, for example, chromate pigment, several ofall of which are known to the skilled of the art, may be employed in thecoating compositions of the invention.

Di- and polyhydroxy compounds of diverse character may be employed alsoin the composition of the invention to modify the properties of thecomposition (i.e. the properties prior to or following cure) as well asto act as solvent, including reactive solvent, for solubilizing thecrosslinking composition. Thus, for example, these compounds may impartincreased flexibility or reduce cratering in spray-applied cured filmsof the crosslinking composition of the invention. Exemplary hydroxycompounds include ethylene glycol, dipropylene glycol, 1,6-hexanediol,and polycaprolactone diols. Another class of glycols includes hydroxyterminated polybutadienes, hydrogenated bis-phenol-A, such hydroxycompounds being of generally hydrophobic character and molecular weightsof about preferably 100-5000, number average. Higher boiling solvents(e.g., boiling point above about 180° C. as 190°-250°) that are of polarcharacter may tend to interact with the resinous components ofcrosslinking composition and thereby allow higher solids content. Ifsuch hydroxy functional compounds are included in the composition of theinvention, then crosslinking agent reactive with hydroxy functionality,such as described above, may be employed, preferably in stoichiometicamount.

As noted above, pigments may be used in the compositions of theinvention in accordance with known techniques. Pigments are employedmost typically, for example, to enhance the efficacy of compositionsemployed as coating compositions over corrosion susceptible substrates.Chromate pigments, in particular, have been used to enhance corrosionprotection. It is, however, a significant advantage of the presentinvention that chromate pigments need not be employed in compositionsemployed as such coating compositions over corrosion susceptiblesubstrates. Cured coating of the invention are highly alkali resistantand provide excellent corrosion protection even without chromatepigments. Such pigments and others can be employed, however, and may bedesirable for aesthetic purposes. Exemplary pigments include titaniumdioxide, silica, carbon black, and barytes and are employed typically atpigment:binder weight ratios of about 40:60 to about 60:40.

It is one characterizing aspect of the present invention that thesubstituent groups on the diene functionality and on the dieneophilefunctionality of the aminoepoxy resins employed in the compositions ofthe invention can be selected to provide the desired degree ofreactivity, that is, cure response. In particular, the degree ofreactivity is increased by diene moiety substitution groups which, innet effort, are electron donating, that is, which decrease the electronaffinity of the diene functionality conjugated double bond. Thus,reactivity is increased by substituent groups such as, for example,amine and ether linkages, sulfoxide, sulfone, urethane and the like.Similarly, it will be understood by the skilled of the art in view ofthe present disclosure, that the shelf stability of the composition isenhanced by ene moiety substitution groups which, in net effect, areelectron withdrawing, that is, which increase the electron affinity ofthe ene functionality double bond. Thus, for example, shelf life isincreased by electron withdrawing diene substitution groups such asnitro, cyano, ester ##STR11## nitrile, carbonyl, straight, branched orcyclo alkyl or cyclo alkyl or alkylene, arylene, aralkylene, --O--,--NR--, --S and the like.

It will be within the ability of those skilled in the art, in view ofthe present disclosure, to select diene substituent groups whichprovide, in net effect, the desired compromise between shelf stabilityand reactivity. It generally is preferred that no electron withdrawinggroup(s) be substituted directly on any carbon of either dienefunctionality double bond, nor on any adjacent or next adjacent atom. Incertain applications, however, a composition of the invention mayrequire extended shelf life or for some other reason call for ortolerate diene functionality comprising electron withdrawingsubstitution groups on the diene moiety.

Applications

As noted above, the crosslinking composition of the invention is usefulin a variety of applications including, especially, as a coatingcomposition to provide an aesthetic and/or protective film on asubstrate. In particular, such crosslinkable composition of theinvention can be formulated into a variety of primer formulationsincluding both aqueous primer formulations and non-aqueous primerformulations. Such primers can be used as coatings for bare or treatedsteels (e.g., conversion coated with phosphates) as well as for guidecoats over primers which were previously deposited, for example, byelectrodeposition. Conventional modifying ingredients can be used insuch primer formulations including, for example, flow control agents,pigments, pigment dispersents, thixotropes, anti-cratering aids,photo-stabilizers and the like, as indicated above.

Solvent Based Primers

Compositions of the invention can be dispersed in organic solvent andapplied to a substrate, for example a ferrous metal substrate, accordingto well known techniques such as by spray, curtain, dip and othercoating application methods. It has been found that solvent basedcoating compositions of the invention comprising diene functional andblocked dieneophile functional aminoepoxy resins modified with hydroxyfunctional secondary amine modifying agent and the butadieneacrylonitrile copolymer resin second modifying agent, as disclosedabove, provide coatings having exceptionally good adhesion andresistance to corrosion. For solvent based coatings to be applied byspray application methods, the diene functional aminoepoxy resin and thedieneophile functional aminoepoxy resin each preferably are of numberaverage molecular weight about 1000-3000. It will be within the abilityof those skilled in the art to determine a suitable solvent and amountof same for a given coating composition of the invention, for a givenapplication. It will be understood that any solvent allowed to remain inthe cured coating should be inert to avoid adverse effects upon thecured coating or upon another coating used in conjunction with it,during the curing process or thereafter. Preferably the cured coating issubstantially free of solvent. Sufficient solvent is used to reduce theviscosity of the coating composition to a level suitable for applicationto the substrate in the desired manner. Thus, for example, for acomposition to be used as a spray-applied primer coating composition, itis preferred that sufficient solvent be used to reduce the viscosity ofthe coating composition to about 25-35 seconds, No. 4 Ford Cup at 27° C.(80° F.).

Solvent based coating compositions according to the invention are curedby heating same to a sufficient temperature for a sufficient time todrive off the solvent, to de-block the dieneophile functionality, and tocause reaction of the diene functionality with the de-blockeddieneophile functionality. Thus, for example, a solvent based coatingcomposition comprising the crosslinkable composition of the inventionaccording to preferred embodiments described above, applied by spraytechniques to the surface of an automotive vehicle body panel as aprimer coat would be cured by heating to a temperature above about 130°C. more preferably about 135°-180° C. for approximately 15-30 minutes.

Water Based Coating Compositions

The crosslinkable composition of the present invention is especiallyadvantageous for use in a water based coating composition. It has beenfound that coating compositions of the invention comprising the twoco-reactive aminoepoxy resins modified with the hydroxy functionalsecondary amine modifying agent and the butadiene acrylonitrilecopolymer second modifying agent are more easily dispersed into aqueoussolvent and provide more stable aqueous dispersions. In addition,electrodeposited coatings of such compositions are found to provideexceptionally good adhesion and resistance to corrosion.

For dispersion into aqueous solvent, the diene functional aminoepoxyresin and dieneophile functional aminoepoxy resin are at least partiallyneutralized by acid, preferably weak organic acid such as formic acid,acetic acid, which is generally preferred, latic acid, butryric acid orthe like or a compatible mixture of any of them. Additional suitableneutralizing acids (often referred to as "solubilizing acid") are knownto the skilled of the art and will be apparent in view of the presentdisclosure. The at least partially neutralized resin is dispersed intowater, preferably de-ionized water for use either in spray applicationmethods, flow coating, etc. or electrodeposition methods. Cured coatingsresulting from such methods are found to provide exceptionally good flowcharacteristics resulting in smooth and otherwise aesthetically superiorfilms having exceptionally good solvent and humidity resistance. Thecured coatings were also found to be highly alkali resistant and thus,to provide exceptionally good corrosion protection to the underlyingsubstrate. Water based coating compositions according to the inventioncan be employed in spray application techniques. Thus, for example, theycan be employed as a spray-applied primer coat for automotive vehiclebody panels.

According to one most preferred embodiment, coating compositions of theinvention can be applied to the surface of a substrate byelectrodeposition techniques. According to this embodiment, thecrosslinkable coating composition, as described above, is at leastpartially, and preferably substantially totally neutralized withsolubilizing acid and thereafter dispersed into de-ionized water orwater/organic solvent mixture to a concentration of about 5-25 weightpercent, more preferably about 10-15 weight percent. The resulting waterbased composition can be used as a cathodic electrocoat composition.That is, the coating comprising the crosslinkable resin and crosslinkingagent, catalysts etc., if any, will deposit upon the workpiece acting asthe cathode according to known electrodeposition systems and techniques.For coating compositions adapted for cathodic electrodeposition, thediene functional aminoepoxy resin is preferably of number averagemolecular weight about 1000-12000, and the blocked dieneophilefunctional aminoepoxy resin is preferably of number average molecularweight about 1000-9000.

Cathodic electrodeposition according to the present invention is donepreferably at voltages of about 1-500 volts, more preferably about200-400 volts. Subsequent to electrodeposition, the coating on thesubstrate is heated to above about 130° C., more preferably about135°-180° C. for a time sufficient to effect the diene/dieneophilereaction and to drive off substantially the entire aqueous solventcontent of the coating. In general, it will be within the ability ofthose skilled in the art to select suitable electrodeposition voltageand baking temperatures and like process parameters in view of theparticular application involved.

Such aqueous solvent based coating compositions can comprise a mixtureof water and water compatible solvent and diluents such as ethyleneglycols and alkylated glycols, for example oxygenated solvents such asCellosolves and carbitols and the like or a compatible mixture of any ofthem. For use as spray primers, for example, such water based coatingcompositions can be formulated with high levels of water, for example,greater than about 10%, such as about 30-50% by weight. Obviously, theparticular time and temperatures necessary to effect curing of thecoating will depend upon the particular resins employed in the coatingcompositions and will depend upon the thickness of the coating, the useof catalysts, and like parameters familiar to the skilled of the art.

The invention will be further understood by referring to the followingdetailed examples. It should be understood that these examples arepresented by way of illustration and not by way of limitation. Unlessotherwise specified, all references to "parts" are intended to meanparts by weight.

EXAMPLE I

This example illustrates the preparation of a diene functionalizedaminoepoxy resin incorporating an alkanolamine modifying agent, a lowmolecular weight aromatic epoxy resin and a secondary amine terminatedbutadiene acrylonitrile copolymer resin as a second modifying agent.Thus, 29.4 g (0.3 mole) furfuryl amine is added to a solution of 152 g(0.8 mole epoxide) of Epon 828 (trademark, Shell Chemical Co.;diepoxide) in 158 g of 1:1 mixture of Cellosolve and hexyl Cellosolve at60° C. After 11/2 hours, 19.95 g (0.19 mole) diethanolamine was addedand the reaction was allowed to continue for 2 hours at 120° C. Then 36g (0.01 mole) ATBN 1300×16 (trademark, B. F. Goodrich; secondary amineterminated butadiene acrylonitrile copolymer resin) was added andallowed to react for 4 hours at 120° C. The reaction product was thencooled to room temperature and stored for future use.

EXAMPLE II

This example illustrates the preparation of a mono-primary aminefunctional blocked dieneophile. Accordingly,3,6-endoxo-1,2,3,6-tetrahydrophthalic anhydride was first prepared bycombining 68 g (1 mole) furan with 98 g (1 mole) maleic anhydride in 166g methyl ethyl ketone. The initially clear solution was stirred at roomtemperature; a mild exotherm and the formation of a white solid wasobserved. After stirring at room temperature for 4-6 hours, the solidswere isolated by filtration, washed with cold methyl ethyl ketone anddried. To form the mono-primary amine functional blocked dieneophile,166 g (1 mole) of 3,6-endoxo-1,2,3,6-tetrahydrophthalic anhydride wasadded to a solution of 170 g (1 mole) isophorone diamine in 300 gdimethoxy ethane (DME). During the initial addition, the anhydridedissolved in the reaction medium and a slight exotherm was noted. Within4-6 hours, the precipitation of the monoprimary amine functional blockeddieneophile had occurred resulting in the formation of a fine white,water soluble solid after a thorough rinse with DME. The product wasstored for future use.

EXAMPLE III

This example illustrates the preparation of blocked dieneophilefunctional aminoepoxy resin incorporating a low molecular weight epoxyresin, diethanol amine modifying agent and secondary amine terminatedbutadiene acrylonitrile copolymer resin. A mixture of 70 g (0.2 mole) ofthe monoprimary amine functional blocked dieneophile prepared in ExampleII is combined with 138 g (0.7 moles epoxide) Epon 828 and 30.45 (0.29moles) diethanolamine in 21 g water and 80 g butanol. The reactionmixture is heated at 80° C. for 4 hours. Then 36g ATBN - 1300×16 isadded and the reaction is allowed to continue for 6 hours at 80° C. Thereaction product is cooled and stored.

EXAMPLE IV

This example illustrates the preparation of an unpigmented electrocoatbath formulation. Accordingly, 64.3 g of of diene functionalized amineepoxy resin prepared according to Example I is combined with 39 g of thedieneophile functionalized aminoepoxy resin of Example III and 6 gglacial acetic acid. The resulting mixture was heated to 40°-50° C. and363 g deionized water is added gradually with rapid mixing with adispersator. After all water had been added, the resulting translucentdispersion was cooled and mixed overnight at room temperature. Theresulting dispersion was filtered, and electrodeposited on steel panelsat 150-200 volts. The deposited panels, after being baked at 180° C. for30 minutes provide smooth coatings which show good corrosion resistance.

EXAMPLE V

This example illustrates the preparation of a pigmented electrocoat bathformulation. This preparation involves a two-part process.

Part A--Mill Base

Materials:

35 g diene functional aminoepoxy resin of Example I

21 g aluminum silicate

6 g white lead

3 g carbon black

35 g 1,2-dimethoxy ethane

The above materials are combined and the pigments are dispersed to aHegman Gage reading of greater than 7 by grinding with metal shot.

Part B--Dispersion/Primer Preparation

Materials:

58 g diene functional aminoepoxy resin of Example I

50 g dieneophile functional aminoepoxy resin of Example III

72 g Mill Base (Part A)

9.86 g glacial acetic acid

522.7 g deionized water

The above materials, except for the water, are mixed together thoroughlyand heated to 50°-60° C. The water is then added slowly while mixingwith a dispersator. After all the water is added, the dispersion iscooled to room temperature and mixed overnight. The resolutingelectrocoat bath is filtered and electrodeposited on steel panels at150-200 volts. The deposited panels are baked at 180° C. for 30 minutesto provide a coating showing good corrosion resistance.

EXAMPLE VI

This example illustrates the use of mixed epoxy resins for thepreparation of diene functional aminoepoxy resin. Thus, the procedure ofExample I is followed using the following materials:

100 g Epon 1001 (trademark, Shell Chemical Co.; diepoxide)

38 g Epon 828 (trademark, Shell Chemical Co.; diepoxide)

29.4 g Furfuryl Amine

19.95 g Diethanol Amine

36.09 g ATBN 1300×16 (trademark B. F. Goodrich Co.)

79.0 g Cellosolve

79.0 g hexyl Cellosolve

The resulting resin is cooled and stored.

EXAMPLE VII

This example illustrates the use of a straight chain aliphatic diaminein the preparation of blocked dieneophile functional aminoepoxy resin.Thus, the procedure of Example II is repeated using 116 g (1 mole)1,6-hexadiamine instead of isophorone diamine. The resulting product isused in the procedure of Example III in place of the product of ExampleII. The product is blocked dieneophile functional aminoepoxy resinsuitable for use in compositions according to the invention.

EXAMPLE VIII

This example illustrates the use of unsaturated lactones in thepreparation of a monoprimary amine functional blocked dieneophile. Thus,the procedure of Example II is repeated except that one mole (98 g) ofa-angelicalactone (4-hydroxy-3-pentenoic acid γ-lacone) is used in placeof maleic anhydride. The resulting product is used in the procedure ofExample III in place of the product of Example II. The product isblocked dieneophile functional aminoepoxy resin suitable for use incompositions according to the invention.

EXAMPLE IX

This example illustrates the preparation of solvent based coatingformulations according to the invention.

Part A--Mill Base

Materials:

35 g diene functionalized aminoepoxy resin of Example I

21 g aluminum silicate

6 g white lead

3 g carbon black

35 g Cellosolve

The above materials were combined and the pigments were dispersed to aHegman Gage reading of greater than 7 by grinding with metal shot. Themill base is then incorporated into coating formulation by thoroughmixing with:

Materials:

58 g diene functional aminoepoxy resin of Example I

50 g blocked dieneophile functional aminoepoxy resin of Example III

36 g mill base (Part A)

250 g xylene : ethoxy ethanol (1:1)

The resulting solvent based composition can be applied to a substrate toproduce a heat-curable coating theron.

EXAMPLE X

This example illustrates the preparation of blocked dieneophilefunctional aminoepoxy resin incorporating a low molecular weight epoxyresin and diethanol amine modifying agent. A mixture of 70 g (0.2 mole)of the monoprimary amine functional blocked dieneophile prepared inExample II was combined with 138 g (0.7 moles epoxide) Epon 828(trademark, Shell Chemical Co.; diepoxide) and 31 g (0.3 moles)diethanol amine in 21 g water and 50 g butanol. The reaction mixture washeated at 80°-90° C. until no epoxide functionality was detected byinfrared spectoscopy. The reaction product was cooled and stored.

EXAMPLE XI

This example illustrates the preparation of an unpigmented electrocoatbath formulation. Accordingly, 64.3 g of diene functionalized aminoepoxyresin prepared according to Example I is combined with 39 g of thedieneophile functionalized aminoepoxy resin of Example X and 6 g glacialacetic acid. The resulting mixture is heated to 40°-50° C. and 363 gde-ionized water is added gradually with rapid mixing with adispersator. After all water has been added, the resulting translucentdispersion is cooled and mixed overnight at room temperature. Theresulting dispersion is filtered, and electrodeposited on steel panelsat 150-200 volts. The coated panels are baked at 100° C. for 30 minutesto provide smooth coatings which show good corrosion resistance.

In view of this disclosure, many modifications of the invention will beapparent to those skilled in the art. It is intended that all suchapparent modifications fall within the true scope of this invention andbe included within the terms of the appended claims.

Industrial Applicability

It will be apparent from the foregoing that this invention hasindustrial applicability as a coating composition, especially as acathodic electrodeposition primer coating composition for sheet steeland the like used in automotive vehicles, household appliances and thelike, and other applications where the coating composition desirably hasexcellent storage stability and the cured coating desirably providesexcellent humidity and solvent resistance to protect the substrateagainst corrosion, wear and the like.

We claim:
 1. A crosslinkable composition of matter comprising first andsecond resins,said first resin being substantially gel-free dienefunctional aminoepoxy resin of number average molecular weight (Mn)about 1000-18,000, comprising the reaction product of diepoxide reactantwith first reactant comprising amine functional conjugated diene chainextending reactant selected from the group consisting of di-secondaryamine functional bis-diene, mono-primary amine functional diene, and amixture of any of them, said second resin being substantially gel-freeblocked dieneophile functional aminoepoxy resin, other than said dienefunctional aminoepoxy resin, having number average molecular weight (Mn)about 1000-18,000, comprising the reaction product of diepoxide reactantwith second reactant comprising amine functional blocked dieneophilechain extending reactant selected from the group consisting ofdi-secondary amine functional bis-blocked dieneophile, mono-primaryamine functional blocked dieneophile, and a mixture of any of them, atleast one of said first reactant and said second reactant furthercomprising modifying agent comprising hydroxy functional secondaryamine, and at least one of said first reactant and said secondaryreactant further comprising second modifying agent selected from thegroup consisting of secondary amine terminated butadiene acrylonitrilecopolymer resin, carboxy terminated butadiene acrylonitrile copolymerresin, and any mixture thereof, said second modifying agent havingnumber average molecular weight about 1400-4400 and amine or carboxy,respectively, equivalent weight of about 700-2200, said compositionfurther comprising crosslinking agent reactive with hydroxyfunctionality.
 2. The crosslinkable composition of claim 1, wherein saidfirst reactant and said second reactant each comprises said modifyingagent.
 3. The crosslinkable composition of claim 2, wherein for each ofsaid diene functional aminoepoxy resin and said blocked dieneophilefunctional aminoepoxy resin the molar equivalent ratio of modifyingagent secondary amine functionality to diepoxide reactant epoxyfunctionality is from about 0.1:1 to about 0.2:1, respectively.
 4. Thecrosslinkable composition of claim 1, wherein said first reactant andsaid second reactant each comprises said second modifying agent.
 5. Thecrosslinkable composition of claim 4, wherein said second modifyingagent contributes about 1-30 percent by weight of said diene functionalaminoepoxy resin and said blocked dieneophile functional aminoepoxyresin.
 6. The crosslinkable composition of claim 1, wherein said firstreactant and said second reactant each comprises said modifying agentand said second modifying agent.
 7. The crosslinkable composition ofclaim 6, wherein for each of said diene functional aminoepoxy resin andsaid blocked dieneophile functional aminoepoxy resin the molarequivalent ratio of modifying agent secondary amine functionality todiepoxide reactant epoxy functionality is from about 0.1:1 to about0.2:1, respectively, and said second modifying agent contributes about1-30 weight percent of each said aminoepoxy resin.
 8. The crosslinkablecomposition of claim 1, wherein said modifying agent is selected fromthe group consisting of alkylalkanolamine, dialkanolamine,N-alkanolaniline, and a mixture of any of them, wherein each alkyl andalkanol moiety has from one to about ten carbons.
 9. The crosslinkablecomposition of claim 1, wherein said modifying agent consistsessentially of diethanolamine.
 10. The crosslinkable composition ofclaim 1, wherein said diepoxide reactant for said diene functionalaminoepoxy resin and said blocked dieneophile functional aminoepoxyresin each is selected independently from the group consisting ofBisphenol A-epichlorohydrin epoxy resin, Novolak epoxy resin, aliphaticepoxy resin and a compatible mixture of any of them.
 11. Thecrosslinkable composition of claim 1, wherein said amine functionalconjugated diene reactant consists essentially of mono-primary aminefunctional diene.
 12. The crosslinkable composition of claim 11, whereinsaid amine functional diene reactant is selected from those of thegeneral formula: ##STR12## wherein R³ is a divalent organic linkingmoiety containing no ester groups and no functionality substantiallyreactive with the diepoxide reactant.
 13. The crosslinkable compositionof claim 11, wherein said amine functional diene reactant is selectedfrom the group consisting of furfuryl amine,2-aminomethyl-1,3-butadiene, and a mixture thereof.
 14. Thecrosslinkable composition of claim 1, wherein said first reactantfurther comprises a mono-functional end-capping reactant bearing asingle functionality substantially reactive with epoxy functionality.15. The crosslinkable composition of claim 14, wherein saidmonofunctional end-capping reactant is selected from the groupconsisting of mono-secondary amine functional diene, monohydroxyfunctional diene, and a compatible mixture of any of them.
 16. Thecrosslinkable composition of claim 14, wherein said monofunctionalend-capping reactant is selected from the group consisting of furfurylalcohol, 2-hydroxymethyl-1,3-butadiene, and a mixture thereof.
 17. Thecrosslinkable composition of claim 1, wherein said amine functionalblocked dieneophile reactant consists essentially of mono-primary aminefunctional blocked ene.
 18. The crosslinkable composition of claim 1,wherein said amine functional blocked dieneophile reactant consistsessentially of amino maleamic acid.
 19. The crosslinkable composition ofclaim 1, wherein said amine functional blocked dieneophile reactantcomprises the reaction product of diamine with3,6-endoxo-1,2,3,6-tetrahydrophthalic anhydride.
 20. The crosslinkablecomposition of claim 1, wherein said amine functional blockeddieneophile reactant comprises the reaction product of (i) diamine and(ii) conjugated diene blocking agent, with (iii) ene reactant selectedfrom the group consisting of maleic anhydride, unsaturated lactone ofthe general formula: ##STR13## wherein each R' is selected independentlyfrom H, C₁ -C₅ alkyl, and C₁ -C₅ hydroxyalkyl, and y is from 1 to about4, and a compatible mixture of any of them.
 21. The crosslinkablecomposition of claim 20, wherein said diamine is selected from those ofthe general formula H₂ N--R⁵ --NH₂, wherein R⁵ is a divalent organic C₂-C₁₅ linking moiety which is substantially unreactive with saiddiepoxide, said ene reactant, and said diene blocking agent.
 22. Thecrosslinkable composition of claim 21, wherein said diamine is selectedfrom the group consisting of branched, straight, and cyclic aliphaticdiamines, aromatic diamines, arylaliphatic diamines, and a compatiblemixture of any of them.
 23. The crosslinkable composition of claim 22,wherein said diamine is selected from the group consisting of isophoronediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine,1,6-hexanediamine, 1,2-ethylenediamine, toluene diamine, and acompatible mixture of any of them.
 24. The crosslinkable composition ofclaim 20, wherein said conjugated diene blocking agent is selected fromthe group consisting of conjugated aliphatic, cyclic aliphatic andheterocyclic aliphatic dienes and a mixture of any of them, wherein saiddiene is substantially unreactive with said diamine and, issubstantially unreactive with said ene reactant except with the enefunctionality thereof.
 25. The crosslinkable composition of claim 20,wherein said conjugated diene blocking agent is selected from the groupconsisting of furan, conjugated cycloalkyadiene, conjugated C₄ -C₁₀alkadiene, and a mixture of any of them.
 26. The crosslinkablecomposition of claim 1, wherein at least one of said first reactant andsaid second reactant further comprises a monofunctional end-cappingreactant bearing a single functionality substantially reactive withepoxy functionality of said diepoxide reactant, and which is otherwisesubstantially unreactive with said diepoxide reactant and substantiallyunreactive with said first reactant and said second reactant.
 27. Thecrosslinkable composition of claim 26, wherein said first reactantcomprises end-capping reactant having the formula: ##STR14## wherein: Ris a monohydroxy functional hydrocarbon moiety or a mono-aminefunctional hydrocarbon moiety, andX⁰ is ##STR15## or the like, whereinR¹ is hydrogen, straight, branched or cyclo alkyl, aryl, or arylalkyl,and each R² is the same or different and is selected from hydrogen,straight, branched or cyclo alkyl, aryl, or arylalkyl, and X¹, X², X³,X⁴ and X⁵ are the same or different and each is hydrogen, straight,branched or cyclo alkyl, aryl, or arylakyl, or X¹ and X⁵ together arealkylene, --O--, or --NR¹ -- wherein R¹ is as defined above.
 28. Thecrosslinkable composition of claim 26, wherein said first reactantcomprises end-capping reactant selected from the group consisting ofmonohydroxy functional conjugated dienes of number average molecularweight about 70-300, and mixtures thereof.
 29. The crosslinkablecomposition of claim 28, wherein said end-capping reactant is selectedfrom the group consisting of furfuryl alcohol,2-hydroxymethyl-1,3-butadiene, and mixtures thereof.
 30. Thecrosslinkable composition of claim 26, wherein said second reactantcomprises end-capping reactant selected from the group consisting ofmono-amine functional blocked dieneophile, monohydroxy functionalblocked dieneophile, and a mixture of any of them.
 31. The crosslinkablecomposition of claim 30, wherein said end-capping reactant consistsessentially of the reaction product of blocking agent selected from thegroup consisting of furan, conjugated cycloalkadiene and a mixture ofany of them, with monohydroxy functional dieneophile selected from thegroup consisting of hydroxypropyl methacrylate, methylol maleimide, anda mixture thereof.
 32. The crosslinkable composition of claim 30,wherein said monofunctional end-capping reactant is selected from thegroup consisting of furfuryl alcohol, 2-hydroxymethyl-1,3-butadiene, anda mixture thereof.
 33. The crosslinkable composition of claim 1, whereinsaid second modifying agent has number average molecular weight of about3400-3600 and amine or carboxy, respectively, equivalent weight of about800-1200.
 34. The crosslinkable composition of claim 1, wherein saidsecond modifying agent comprises the polymerization reaction product ofacrylonitrile monomer with butadiene monomer, said acrylonitrilereacting in sufficient amount to contribute about 10-27 percent byweight of said second modifying agent.
 35. The crosslinkable compositionof claim 1, wherein said crosslinking agent is selected from the groupconsisting of aminoplast crosslinking agents, poly-blocked isocyanatecrosslinking agents, and a mixture of any of them.
 36. A solvent basedcoating composition comprising first and second resins,said first resinbeing substantially gel-free diene functional aminoepoxy resin of numberaverage molecular weight about 1000-3000, comprising the reactionproduct of (1) second modifying agent consisting of secondary amineterminated butadiene acrylonitrile copolymer resin of number averagemolecular weight about 1400-4400 and amine equivalent weight about700-2200, with (2) the reaction product of a molar equivalent excess ofdiepoxide reactant consisting essentially of Bisphenol A-epichlorlhydrindiepoxide resin with (a) amine functional diene chain extending reactantselected from the group consisting of furfuryl amine,2-aminomethyl-1,3-butadiene, and a mixture thereof, (b) monofunctionalend-capping reactant selected from the group consisting of furfurylalcohol, 2-hydroxymethyl-1,3-butadiene and a mixture thereof, and (c)modifying agent consisting of C₂ -C₅ dialkanolamine, and said secondresin being substantially gel-free blocked dieneophile functionalaminoepoxy resin of number average molecular weight about 1000-3000,comprising the reaction product of (1) amine functional blockeddieneophile chain extending reactant comprising the reaction product of(a) diamine selected from the group consisting of isophorone diamine,1,3-propanediamine, 1, 4-butanediamine, 1,5-pentanediamine,1-6-hexanediamine, 1,2-ethylenediamine, toluene diamine and any mixturethereof, and (b) conjugated diene blocking agent selected from the groupconsisting of furan, conjugated cycloalkadiene, conjugated C₄ -C₁₀alkadiene, and a mixture of any of them, with (c) ene reactant selectedfrom the group consisting of maleic anhydride, unsaturated lactone ofthe general formula: ##STR16## wherein each R' is selected independentlyfrom H, C₁ -C₅ alkyl, and C₁ -C₅ hydroxyalkyl, and y is from 1 to about4, and a compatible mixture of any of them, with (2) the reactionproduct of a molar equivalent excess of diepoxide reactant consistingessentially of Bisphenol A-epichlorohydrin diepoxide resin with (a)second modifying agent consisting of secondary amine terminatedbutadiene acrylonitrile copolymer resin of number average molecularweight about 1400-4400 and amine equivalent weight about 700-2200, (b)monofunctional end-capping reactant comprising the reaction product ofconjugated diene blocking agent selected from the group consisting offuran, conjugated cycloalkadiene, conjugated C₄ -C₁₀ alkadiene and amixture of any of them, with monohydroxy functional dieneophile selectedfrom the group consisting of hydroxypropyl methacrylate, methylolmaleimide, and a mixture thereof, and (c) modifying agent selected fromthe group consisting of C₂ -C₅ dialkanolamine, said coating compositionfurther comprising organic solvent and crosslinking agent reactive withhydroxy functionality.
 37. The solvent based crosslinkable compositionof claim 36 wherein said crosslinking agent is selected from the groupconsisting of aminoplast crosslinking agent, polyblocked isocyanatecrosslinking agent, and a mixture thereof.
 38. A crosslinkablecomposition of matter adapted for use in electrodeposition of coatingson a substrate, which composition comprises first and second chainextended diepoxide resins,said first resin being substantially gel-freediene functional aminoepoxy resin of number average molecular weightabout 1000-12,000, at least partially neutralized with solubilizing acidselected from the group consisting of acetic acid, lactic acid, formicacid, butyric acid, and a compatible mixture of any of them, comprisingthe reaction product of (1) second modifying agent consisting ofsecondary amine terminated butadiene acrylonitrile copolymer resin ofnumber average molecular weight about 1400-4400 and amine equivalentweight about 700-2200, with (2) the reaction product of a molarequivalent excess of diepoxide reactant consisting essentially ofBisphenol A-epichlorohydrin diepoxide resin with (a) amine functionaldiene chain extending reactant selected from the group consisting offurfuryl amine, 2-aminomethyl-1,3-butadiene, and a mixture thereof, (b)optionally, monofunctional end-capping reactant selected from the groupconsisting of furfuryl alcohol, 2-hydroxymethyl-1,3-butadiene, and amixture thereof, and (c) modifying agent consisting of C₂ -C₅dialkanolamine, and said second resin being substantially gel-freeblocked dieneophile functional aminoepoxy resin of number averagemolecular weight about 1000-9000, at least partially neutralized withsolubilizing acid selected from the group consisting of acetic acid,lactic acid, formic acid, butyric acid, and a compatible mixture of anyof them, comprising the reaction product of (1) amine functional blockeddieneophile chain extending reactant comprising the reaction product of(a) diamine selected from the group consisting of isophorone diamine,1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine,1-6-hexanediamine, 1,2-ethylenediamine, toluene diamine and any mixturethereof, and (b) conjugated diene blocking agent selected from the groupconsisting of furan, conjugated cycloalkadiene, conjugated C₄ -C₁₀alkadiene, and a mixture of any of them, with (c) ene reactant selectedfrom the group consisting of maleic anhydride, unsaturated lactone ofthe general formula: ##STR17## wherein each R' is selected independentlyfrom H, C₁ -C₅ alkyl, and C₁ -C₅ hydroxyalkyl, and y is from 1 to about4, and a compatible mixture of any of them, with (2) the reactionproduct of a molar equivalent excess of diepoxide reactant consistingessentially of Bisphenol A-epichlorohydrin diepoxide resin, with (a)monofunctional end-capping reactant comprising the reaction product ofconjugated diene blocking agent selected from the group consisting offuran, conjugated cycloalkadiene, conjugated C₄ -C₁₀ alkadiene and amixture of any of them, with monohydroxy functional dieneophile selectedfrom the group consisting of hydroxypropyl methacrylate, methylolmaleimide, and a mixture thereof, and (b) modifying agent selected fromthe group consisting of C₂ -C₅ dialkanolamine, which crosslinkablecomposition further comprises crosslinking agent reactive with hydroxyfunctionality and aqueous slovent, said at least partially neutralizeddiene functional aminoepoxy resin and said at least partiallyneutralized bolcked dienephile functional aminoepoxy resin and saidcrosslinking agent being dispersed together in said aqueous solvent. 39.The crosslinkable composition of claim 38, wherein said crosslinkingagent is selected from the group consisting of aminoplast crosslinkingagents, poly-blocked isocyanate crosslinking agent, and a mixturethereof.